Identification and characterization of genes encoding sex pheromone cAM373 activity in Enterococcus faecalis and Staphylococcus aureus

The sex pheromone cAM373 of Enterococcus faecalis and the related staph -cAM373 of Staphylococcus aureus were found to correspond to heptapeptides located within the C-termini of the signal sequences of putative prelipoproteins. The deduced mature forms of the lipoproteins share no detectable homology and presumably serve unrelated functions in the cells. The chromosomally encoded genetic determinants for production of the pheromones have been identified and designated camE (encoding cAM373) and camS (encoding staph -cAM373). Truncated and full-length clones of camE were generated in Escherichia coli , in which cAM373 activity was expressed. In E. faecalis , insertional inactivation in the middle of camE had no detectable phenotypic effects on the pheromone system. Establishment of an in frame translation stop codon within the signal sequence resulted in reduction of cAM373 activity to 3% of normal levels. The camS determinant has homologues in Staphylococcus epidermidis , Bacillus subtilis and Listeria monocytogenes ; however, corresponding heptapeptides present within those sequences do not resemble staph -cAM373 closely. The particular significance of staph -cAM373 as a potential intergeneric inducer of transfer-proficient genetic elements is discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75605/1/j.1365-2958.2002.02922.x.pd

Enterococcal sex pheromone precursors are part of signal sequences for surface lipoproteins

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73811/1/j.1365-2958.2000.01687.x.pd

Enterococcal sex pheromone precursors are part of signal sequences for surface lipoproteins

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73811/1/j.1365-2958.2000.01687.x.pd

Plasmid pAMS1-Encoded, Bacteriocin-Related “Siblicide” in Enterococcus faecalis▿

The Enterococcus faecalis class IIa bacteriocin MC4-1 encoded by the sex pheromone-responding, multiple-antibiotic resistance plasmid pAMS1 exhibits “siblicidal” (sibling-killing) activity under certain conditions. Stabs of plasmid-containing cells on solid medium containing lawns of bacteria of the same (plasmid-containing) strain give rise to zones of inhibition. If the plasmid-containing host also produces gelatinase, bacteriocin cannot be detected

Nucleotide Sequence of the 18-kb Conjugative Transposon Tn916 from Enterococcus faecalis

Conjugative transposon Tn916 from Enterococcus faecalis DS16 encodes tetracycline resistance (Tet M) as well as determinants necessary for its own movement. Determination of the nucleotide sequence of Tn916 has been completed. The element is 18,032 bp in length and has an overall G+C content of 38.8%. Twenty-four potential open reading frames (ORFs) were identified based on sequence analysis. Similarities of the ORFs to other known determinants, which were revealed by database searches, are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31215/1/0000117.pd

Indication of Transposition of a Mobile DNA Element Containing the vat(D) and erm(B) Genes in Enterococcus faecium

The vat(D) and erm(B) genes encoding streptogramin resistance in Enterococcus faecium transferred together, and a direct physical link between erm(B) and vat(D) was detected. Both the vat(D) and erm(B) probes hybridized to fragments of different sizes in the donor and transconjugants, which indicated a transposition event

Bactericidal and Bioactive Dental Composites

Aim: Antimicrobial and bioactive restorative materials are needed to develop a bacteria free environment and tight bond with the surrounding tissue, preventing the spread of secondary caries and thus extending the lifetime of dental restorations. The characteristic properties of new dental bioactive and antibacterial composites are presented in this work. The new composites have been microstructurally characterized and both long and short term properties have been studied.Methods: The Ag-doped sol-gel derived bioactive glass (Ag-BG) was incorporated into resin composite in concentrations 5, 10, and 15 wt.%, to fabricate new Ag-doped bioactive and antibacterial dental composites (Ag-BGCOMP). The microstructural properties and elemental analysis of the developed Ag-BGCOMP was observed. The total bond strength (TBS) was measured immediately and after long term of immersion in medium using microtensile testing. The capability of Ag-BGCOMPs to form apatite layer on their surface after immersion in Simulated Body Fluid (SBF) as well as the bacteria growth inhibition in a biofilm formed by Streptococcus mutans (S. mutans) were evaluated.Results: Homogeneous distribution of Ag-BG particles into the resin composite was observed microstructurally for all Ag-BGCOMPs. The TBS measurements showed non-statistically significant difference between control samples (Ag-BG 0 wt.%) and Ag-BGCOMP specimens. Moreover, the total bond strength between the surrounding tooth tissue and the material of restoration does not present any statistically significant change for all the cases even after 3 months of immersion in the medium. The bioactivity of the Ag-BGCOMPs was also shown by the formation of a calcium-phosphate layer on the surface of the specimens after immersion in SBF. Antibacterial activity was observed for all Ag-BGCOMPs, statistically significant differences were observed between control samples and Ag-BGCOMPs. Accordingly, the number of dead bacteria in the biofilm found to increase significantly with the increase of Ag-BG concentration in the Ag-BGCOMPs.Conclusions: New resin composites with antibacterial and remineralizing properties have been manufactured. Characterization of these materials provides a rationale for future clinical trials to evaluate clinical benefits and outcomes in comparison with currently used dental materials.Significance: The new developed composites could ultimately prevent restoration failure and could advance patients' wellbeing